1. Field of the Invention
The present invention relates to a liquid discharge head for discharging a desired liquid by externally applying energy, and a method for manufacturing the liquid discharge head. The liquid discharge head of the invention can be applied to an ink jet recording head that prints on materials such as paper, cloth, leather, non-woven fabric and OHP sheets, a patterning device or a coating device that attaches a liquid to a solid object, such as a substrate or a plate member. A typical ink jet recording head will now be described.
2. Description of the Related Art
Printers using ink jet recording heads are widely employed for personal computers because they can provide satisfactory printing functions at low cost. Various types of ink jet recording heads have been developed, for example: heads that employ thermal energy to generate bubbles in ink, and use pressure waves produced by the bubbles to discharge ink droplets; heads that employ electrostatic force to attract and discharge ink droplets; and heads that employ pressure waves generated by vibrators, such as piezoelectric elements.
An ink jet recording head that employs a piezoelectric device includes: ink flow paths that communicate with ink discharge openings; and pressure generation chambers that communicate with the ink flow paths. Piezoelectric thin film is adhered to vibration plate film that is deposited on pressure generation chambers, and when a predetermined voltage is applied to the piezoelectric thin film, the film either stretches or contracts. As the piezoelectric thin film stretches or contracts, the vibration plate film vibrates with the piezoelectric thin film, generating a pressure pulse in ink held, under pressure, in the pressure generation chambers. As a result, ink is forced through the ink discharge openings and discharged as droplets.
As requests for higher definition images have increased, ink jet recording heads have become ever more highly integrated, i.e., multiple ink pressure generation chambers and multiple pressure generation sources, such as piezoelectric elements on flow path substrates, have been arranged at higher densities.
In order to better cope with these requests for higher definition images, an example piezoelectric type ink jet recording head is proposed wherein, using a film deposition technique, electrodes and piezoelectric members are formed across the entire surface of a vibration plate, and through the application of a photolithography technique, these electrodes and piezoelectric members are processed in correlation with the ink pressure chambers. In this case, a high density ink jet recording head is obtained by employing both the film deposition technique and the photolithography technique. Further, since an Si substrate and a metal member are respectively employed as a flow path substrate and as an orifice plate, flow paths and orifices can be accurately formed.
Generally, piezoelectric members are formed in correlation with the ink pressure chambers, and have smaller widths than have the ink pressure generation chambers. Furthermore, a dry etching technique using a chlorinated gas has recently been introduced for processing these piezoelectric members. And compared with wet etching, using a hydrofluoric acid solution or an oxidized solution, etching rates and etching shapes can more easily be controlled, enabling accurate processing.
As a method to improve the dielectric strength of a piezoelectric device, Japanese Patent Application Laid-Open No. 2004-186574 discusses a technique for laminating a Pb containing perovskite material and a Pb not containing perovskite material. Furthermore, Japanese Patent Application Laid-Open No. H09-277519 discusses a technique whereby a step shaped piezoelectric layer is formed to cover and protect lower electrodes.
Japanese Patent Application Laid-Open No. 2000-037868 discusses a technique whereby an inter-layer insulating layer is formed between an upper electrode and a lower electrode that are led outside from a piezoelectric device in order to prevent the destruction of a piezoelectric layer.
For an arrangement wherein a lower electrode is not patterned, the lower electrode is employed as an etching stop layer when processing a piezoelectric member using the dry etching method. When this arrangement is used to process a piezoelectric member, the lower electrode is also etched, although only slightly. On the contrary, however, especially when a Pt electrode is employed as a lower electrode and a chlorine gas used for this processing contacts the surface of the Pt electrode, considerable etching of the Pt electrode occurs.
Especially when a hard to etch material, such as lead zirconate titanate (PZT), is employed as a piezoelectric member, the process tends to be performed under an etching condition that there is a strong sputtering connotation. At such a time, when the lower electrode is exposed during the etching of the piezoelectric member, the material for the lower electrode may be sputtered and be attached to the end face of the processed piezoelectric member. The attachment of metal to the end face of the piezoelectric member could cause a short between the upper and lower electrodes and destroy the piezoelectric thin film.
Furthermore, when the lower electrode is exposed near piezoelectric thin film that serves as a driver, when the piezoelectric member is driven, a short may occur between the upper and lower electrodes, or the electrodes or the piezoelectric thin film may be damaged.
As another problem, since a piezoelectric member generally has a high dielectric constant, a piezoelectric device has a large electrostatic capacity and a low response speed relative to a drive wave, so that the timely capture and utilization of a drive wave that will provide an adequately accurate discharge is sometimes not possible. Further, since an electrostatic capacity is not required for electric leads to external wiring, a reduction in the electrostatic capacity is demanded.